Indução e sincronização de estro em ovelhas: desafios e potencial / Estrous induction and synchronization in ewes: challenge and potential

O conhecimento da dinâmica endócrina do ciclo estral permitiu o desenvolvimento de protocolos hormonais, isolados ou associados às técnicas de manejo, para controlar a apresentação do estro e da ovulação. Os protocolos convencionais envolvem dispositivos intravaginais impregnados com progesterona ou progestágenos e prostaglandinas ou seus análogos, em conjunto com gonadotrofina coriônica equina (eCG), visando à produção de folículos saudáveis em um ambiente de baixas concentrações de gonadotrofinas e estrógenos ou luteólise com uma subsequente fase folicular culminando em ovulação. Na indução ou sincronização do momento da ovulação, com os mesmos regimes aplicados em bovinos, são usadas gonadotrofinas (eCG; gonadotrofina coriônica humana; hCG; hormônio folículo estimulante; FSH), GnRH (fator liberador de gonadotrofinas) ou estrógenos. Contudo, mais estudos são necessários para a produção de ovinos em larga escala, do tipo “verde, ético e limpo”, a ativação da reprodução por meio de métodos nutricionais, de manejo ou do uso de menos hormônios exógenos. Esta revisão aborda os métodos que vêm sendo utilizados para sincronização de estro em ovelhas, bem como as alternativas que existem à hormonioterapia.(AU)

The knowledge of estrous cycle endocrine dynamics allowed the development of hormonal protocols, isolated or associated with management techniques to control the onset of estrous and ovulation. Conventional protocols involve intravaginal devices impregnated with progestagens or progestin and prostaglandins or their analogues, in conjunction with equine chorionic gonadotrophin (eCG), yielding healthy follicles in environment of low concentrations of gonadotrophins and oestrogens or a luteolisis with a subsequent follicular phase culminating in ovulation. Synchronization of time or induction of ovulation using the same regimens as applied in cattle, using various gonadotrophins (equine chorionic gonadotrophin - eCG; human chorionic gonadotrophin hCG; stimulate follicle hormone - FSH), GnRH (gonadotrophin releasing factor)or oestrogens. However, more studies are needed for ovine industry on a large scale, such as “green, clean and ethical”, enabling playback through nutritional methods, management or use of exogenous hormones less that it should becomes object of investigation. This review covers the methods that have been used for estrous synchronization in ewes, as well as the alternatives that exist to hormonetherapy.(AU)

Indução e sincronização de estro em ovelhas: desafios e potencial / Estrous induction and synchronization in ewes: challenge and potential

O conhecimento da dinâmica endócrina do ciclo estral permitiu o desenvolvimento de protocolos hormonais, isolados ou associados às técnicas de manejo, para controlar a apresentação do estro e da ovulação. Os protocolos convencionais envolvem dispositivos intravaginais impregnados com progesterona ou progestágenos e prostaglandinas ou seus análogos, em conjunto com gonadotrofina coriônica equina (eCG), visando à produção de folículos saudáveis em um ambiente de baixas concentrações de gonadotrofinas e estrógenos ou luteólise com uma subsequente fase folicular culminando em ovulação. Na indução ou sincronização do momento da ovulação, com os mesmos regimes aplicados em bovinos, são usadas gonadotrofinas (eCG; gonadotrofina coriônica humana; hCG; hormônio folículo estimulante; FSH), GnRH (fator liberador de gonadotrofinas) ou estrógenos. Contudo, mais estudos são necessários para a produção de ovinos em larga escala, do tipo “verde, ético e limpo”, a ativação da reprodução por meio de métodos nutricionais, de manejo ou do uso de menos hormônios exógenos. Esta revisão aborda os métodos que vêm sendo utilizados para sincronização de estro em ovelhas, bem como as alternativas que existem à hormonioterapia.

The knowledge of estrous cycle endocrine dynamics allowed the development of hormonal protocols, isolated or associated with management techniques to control the onset of estrous and ovulation. Conventional protocols involve intravaginal devices impregnated with progestagens or progestin and prostaglandins or their analogues, in conjunction with equine chorionic gonadotrophin (eCG), yielding healthy follicles in environment of low concentrations of gonadotrophins and oestrogens or a luteolisis with a subsequent follicular phase culminating in ovulation. Synchronization of time or induction of ovulation using the same regimens as applied in cattle, using various gonadotrophins (equine chorionic gonadotrophin - eCG; human chorionic gonadotrophin – hCG; stimulate follicle hormone - FSH), GnRH (gonadotrophin releasing factor)or oestrogens. However, more studies are needed for ovine industry on a large scale, such as “green, clean and ethical”, enabling playback through nutritional methods, management or use of exogenous hormones less that it should becomes object of investigation. This review covers the methods that have been used for estrous synchronization in ewes, as well as the alternatives that exist to hormonetherapy.

Effects of flunixin meglumine on reproductive parameters in beef cattle

Flunixin meglumine (FM) has been used as an attempt to inhibit luteolysis in ruminants. The effects of FM on seric concentration of progesterone, pregnancy rate and ovarian status of cows were assessed in this study. Fifty-seven cows were divided into Control Group (CG; n = 30) and Treated Group (TG; n = 27) on an estrus synchronization program involving intramuscular(IM) estradiol benzoate (EB) and intravaginal progesterone-releasing insert. After seven days the intravaginal insert was removed, prostaglandin-F2alpha (PGF2α) IM was given, and then EB was administered 24 h later. Fixed-time artificial insemination (FTAI) was conducted 30 h after EB administration. Animals from the TG received 1.1 mg/kg of FM IM daily between the days 11 and 16 of the estrous cycle (day 0 = FTAI), whereas the animals from the CG received physiological solution. Blood from all animals wascollected on days 0, 6, 9, 11 through 18, and 21. Thirty animals from the Nellore breed were selected for the measurement of serum concentrations of progesterone by radioimmunoassay. Animals which returned to estrus were inseminated again (artificial insemination; AI) and allocated back to their groups. Pregnancy diagnosis was conducted by transrectal ultrasound in either FTAI or AI cows after30 days. The ovarian condition of the nin-pregnant animals was reevalunted 4 days later. Progesterone concentration among the animals from the experimental groups was similar until the day 18 of the estrous cycle (P > 0.05). On day 21, pregnant animals presented higher progesterone concentrations (P < 0.05) than non-pregnant animals from the TG and TN Pregnancy rate was similar among the groups (P > 0.05). However, non-pregnant animals from the TG presented higher (P > 0.05) follicular persistence than that observed for the animals in the CG, 78.6% (11/14) vs. 33.3% (5/15), respectively (P = 0.025). Results indicate that FM administered during the luteolysis period of beef cattle does not influence progesterone concentration and pregnancy rate, although it influences the occurrence of follicular persistence.(AU)

Effects of flunixin meglumine on reproductive parameters in beef cattle

Flunixin meglumine (FM) has been used as an attempt to inhibit luteolysis in ruminants. The effects of FM on seric concentration of progesterone, pregnancy rate and ovarian status of cows were assessed in this study. Fifty-seven cows were divided into Control Group (CG; n = 30) and Treated Group (TG; n = 27) on an estrus synchronization program involving intramuscular(IM) estradiol benzoate (EB) and intravaginal progesterone-releasing insert. After seven days the intravaginal insert was removed, prostaglandin-F2alpha (PGF2α) IM was given, and then EB was administered 24 h later. Fixed-time artificial insemination (FTAI) was conducted 30 h after EB administration. Animals from the TG received 1.1 mg/kg of FM IM daily between the days 11 and 16 of the estrous cycle (day 0 = FTAI), whereas the animals from the CG received physiological solution. Blood from all animals wascollected on days 0, 6, 9, 11 through 18, and 21. Thirty animals from the Nellore breed were selected for the measurement of serum concentrations of progesterone by radioimmunoassay. Animals which returned to estrus were inseminated again (artificial insemination; AI) and allocated back to their groups. Pregnancy diagnosis was conducted by transrectal ultrasound in either FTAI or AI cows after30 days. The ovarian condition of the nin-pregnant animals was reevalunted 4 days later. Progesterone concentration among the animals from the experimental groups was similar until the day 18 of the estrous cycle (P > 0.05). On day 21, pregnant animals presented higher progesterone concentrations (P 0.05). However, non-pregnant animals from the TG presented higher (P > 0.05) follicular persistence than that observed for the animals in the CG, 78.6% (11/14) vs. 33.3% (5/15), respectively (P = 0.025). Results indicate that FM administered during the luteolysis period of beef cattle does not influence progesterone concentration and pregnancy rate, although it influences the occurrence of follicular persistence.

Efeitos da progesterona exógena sobre o desenvolvimento folicular em ovelhas / Effects of exogen progesterone on follicular development in sheep

Avaliaram-se os efeitos da progesterona (P4) sobre o crescimento folicular e na endocrinologia reprodutiva em ovelhas Bergamácia. Quatorze ovelhas sincronizadas com prostaglandinas (PGF2alfa ) foram distribuídas em dois grupos (n=7/grupo): grupo-controle e grupo tratado com progesterona (CIDR) depois da ovulação (dia zero). Desde o dia anterior à aplicação de PG até o dia 10, realizaram-se monitoramentos ultra-sonográficos para estabelecer o crescimento folicular. Amostras de sangue foram colhidas para a determinação de P4 desde o dia anterior à aplicação de PG até o dia 10 depois da ovulação. Para o perfil dos pulsos de hormônio luteinizante (LH), as colheitas de sangue ocorreram em intervalos de 30 minutos por um período de oito horas, nos dias um e seis. As taxas de crescimento diferiram (P<0,001) entre os grupos, 0,91±0,15 e 0,70±0,16mm/dia para os grupos controle e tratado, respectivamente. Os dias do platô dos animais controle e tratados foram de 1,9±0,72 e 2,9±0,45 (P<0,05), respectivamente. As concentrações médias de progesterona (P<0,001) foram diferentes entre os tratamentos. A freqüência dos pulsos diferiu no primeiro dia do ciclo (P<0,01), com valores de 2,55±0,09 pulsos/8 horas no grupo-controle e de 1,49±0,11 pulsos/8 horas no grupo tratado. No sexto dia, o grupo-controle 2,20±0,09 pulsos/8 horas apresentou maior número de pulsos (P<0,05) que o grupo tratado, 1,22±0,11 pulsos/8 horas. Os efeitos inibitórios da progesterona exógena no diâmetro do folículo dominante foram mediados pela redução na freqüência dos pulsos de LH.(AU)

The effects of progesterone (P4) on ovarian follicular growth and reproductive endocrinology were studied. Fourteen ewes, synchronized using prostaglandin (PGF2alpha ), were randomly divided in two groups (n=7/group); control group and progesterone-treated group (CIDR) after ovulation (day zero). From one day before PG injection until day 10, daily ultrasonic examinations were done to establish follicular growth. Blood samples for P4 plasma concentration determinations were collected from one day before PG until day 10 post-ovulation. For profile of LH pulses, blood samples were collected at 30-min intervals for a period of 8h on days one and six. The growth rate was different between groups (P<0.001), being 0.91±0.15 and 0.70±0.16mm/d for control and treated-group, respectively. The lengthened of the static phase for control and treated group were 1.9±0.72 and 2.9±0.45d (P<0.05), respectively. Mean concentrations of P4 (P<0.001) were different between treatments. Differences in LH pulse frequency on day one (P<0.01) were observed with values of 2.55±0.09 pulses/8 h in control group and 1.49±0.11 pulses/8h in treated-group. On day six, control group showed higher values for LH pulse frequency (2.20±0.09 pulses/8h) than treated-group (P<0.05), (1.22±0.11 pulses/8h). In conclusion, the inhibitory effects of exogen P4 on the diameter of dominant follicle was mediated by reduced LH pulse frequency.(AU)

Determinação dos ritmos circadianos e circanuais nas concentrações plasmáticas de testosterona e androstenediona em machos ovinos / Circadian and circannual rhythms determination in testosterone and androstenedione plasma concentrations in ovine males / Determinación de los ritmos circadianos y circanuales en las concentraciones plasmáticas de testosterona y androstenediona en machos ovinos

Estudou-se a estacionalidade reprodutiva de machos ovinos no Estado de São Paulo para estabelecer os ritmos endócrinos circadianos e circanuais, de cinco carneiros Ideal-Polwarth. O sangue foi colhido por venopunção jugular, em um período de 24 horas, sendo as colheitas realizadas de duas em duas horas, a cada dois meses (seis momentos de colheita em um ano), para a obtenção do plasma e avaliação dos níveis de testosterona e androstenediona por radioimunoensaio. As concentrações plasmáticas de androstenediona e testosterona não permitiram a definição de um ritmo circadiano em suas respectivas secreções, porém, demonstraram ritmos circanuais, com níveis mais baixos de junho a outubro e mais elevados de dezembro a abril.(AU)

The reproductive seasonality of ovine males in Sao Paulo State was studied to establish the circadian and circannual endocrine rhythms of 5 Ideal-Polwarth rams. Blood was collected by puncturing the jugular vein for 24 hours with 2-hour intervals every 2 months (6 collections throughout the year) in order to obtain plasma and evaluate testosterone and the androstenedione levels by radioimmunoassay. The Testosterone and androstenedione plasma concentrations did not demonstrate a circadian rhythm in their respective secretions; however, they showed lower levels of circannual rhythms from June to October and higher from December to April.(AU)

Se estudió la estacionalidad reproductiva en machos ovinos en el Estado de São Paulo para determinar los ritmos endocrinos circadianos y circanuales, de cinco moruecos Ideal-Polwarth. La sangre se recogió por venopunción yugular, en un período de 24 horas, con las colectas de dos en dos horas, a cada dos meses (seis colectas en un año), para la obtención del plasma y evaluación de los niveles de la testosterona y androstenediona por el radioimunoensayo. Las concentraciones de la testosterona y androstenediona no permitieron la definición de un ritmo circadiano en sus secreciones, pero demostraron ritmos circanuales, con niveles más bajos de junio hasta octubre y más elevados de diciembre hasta abril.(AU)